The present invention relates to an antenna element based on a slotted wave-guide, a transceiver unit incorporating such an antenna element and methods for operating such antenna elements and transceivers.
Slotted wave-guide aerials are popular in many connections and for many applications. One reason is that they combine the emission and feeder element in one unit, which leads to a space efficient design. Slotted wave-guides are also well suited for mass production and many calculation programs exist for dimensioning such wave-guides.
Slotted wave-guides providing a circular polarisation are known in the art.
JP-07226617 shows a circularly polarised antenna having a linear feeder formed on the surface of a dielectric ground conductor and two slots disposed xc2x145xc2x0 to a feeding line and 90xc2x0 to one another.
In an Article in the IEEE, Transactions on antennas and propagation, Vol. 43, No. 8, August 1995, p 874-876 a radial line slot antenna has been disclosed having a plurality of orthogonally arranged slots, the slots furthermore being arranged in a spiralling pattern.
In FIG. 1, a conventional mobile terminal with transceiver, T, and a conventional vertically polarized base-station antenna, e, and transceiver, f, have been shown. It is assumed that the mobile terminal and the base-station antenna are arranged in a free field.
In a first upright position, a, the antenna of the mobile terminal is parallel to the base-station antenna. In this position, there is an absolute polarisation match and no polarisation loss occurs between the mobile terminal and base-station. If the mobile terminal is positioned at a 45xc2x0 angle with regard to the node antenna, which is indicated in position b, a polarisation mismatch occurs leading to a 3 dB loss in signal power. Moreover, If the mobile terminal is directed at a 90xc2x0 angle to the base-station antenna, as seen in position c, a total polarisation mismatch occurs and no signal is transferred.
In a typical environment in which mobile telephones are operated, multiple obstacles will reflect and scatter the signals between mobile terminal and base station. This means that even though the mobile terminal is put in a 90xc2x0 position with respect to the base-station antenna, some signals will be reflected, whereby the polarisation of the signal will be changed such that it is received at a sufficient signal power level. On the other hand, an absolute polarisation match seldom occurs.
The invention seeks to provide an antenna element in which the polarisation can be controlled arbitrarily and fast.
According to a first aspect of the invention, as defined in claim 1, such a wave-guide is provided.
It is a further object to accomplish an antenna element, which can be produced cost effectively and which is compact.
This object has been accomplished by the subject matter set forth in claim 2.
It is a further object to provide an antenna element in which the polarisation can be controlled in real time.
This object has been accomplished according to claim 3
It is a further object to accomplish a transceiver, which adapts the polarisation with the opposing transceiver with which it communicates.
This object has been achieved by the subject matter defined by claim 15.
It is a further object to accomplish a transceiver in which the polarisation of the transmitted and received waves can be controlled individually and simultaneously.
This object has been accomplished by the subject matter set forth in claim 16.
It is a further object to set forth a method by which the communication between two transceivers can be optimised.
This object is accomplished by the subject matter set forth in claim 17.
It is a further object to accomplish an optimisation of the communication between to transceivers with regard to the quality of the links.
This object has been accomplished by the subject matter set forth in claim 18.
It is a further object to accomplish an airborne radar system being insensitive for disturbances.
This object has been accomplished by the subject matter defined by claim 19.
It is a further object to accomplish a satellite terminal, which optimises quality parameters for the communication.
This object has been accomplished by the subject matter defined by claims 20-22.
Further advantages will appear from the following detailed description of the invention.